Question: $\left[\begin{array} {ccc} 1 & 6 & 9 & 3 \\ 2 & 5 & 8 & 1 \\ 0 & 2 & 2 & 4 \end{array}\right]$ What are the dimensions of the matrix?
Answer: The first dimension is the number of rows in the matrix. There are $3$ rows. The second dimension is the number of columns in the matrix. There are $4$ columns. In conclusion, the dimensions of the matrix are $3\times 4$.